1. Field
Aspects of the present disclosure relate generally to oscillators or signal generators, and more particularly, to a temperature-compensated signal generator for supply voltage monitoring or other purposes.
2. Background
Often, there are situations where a direct current (DC) supply voltage from a power source (e.g., a battery, a voltage regulator, etc.) should be monitored to detect abnormalities in the supply voltage and perform some corrective action (e.g., provide a warning, disable one or more circuits, etc.). Some examples of abnormalities include an over-voltage condition, an under-voltage condition, voltage glitches (intentional and unintentional), etc.
A typical circuit for monitoring a supply voltage for the purpose of detecting abnormalities includes an oscillator (e.g., a ring oscillator) and a frequency-to-digital converter (FDC). The oscillator generates an oscillating signal having a frequency, the frequency being a function of the supply voltage. For example, the frequency of the oscillating signal may increase or decrease with an increase or decrease in the supply voltage, respectively. The FDC generates a digital output code or value indicative of the supply voltage based on the frequency of the oscillating signal generated by the oscillator. By monitoring the digital output code produced by the FDC, abnormalities (e.g., over-voltage condition, under-voltage condition, voltage glitches, etc.) may be detected.
For the supply voltage monitoring circuit to operate accurately, the frequency of the oscillating signal should not vary significantly over an operating temperature range of the circuit. Otherwise, a significant temperature change within the operating range may be misinterpreted as an abnormality in the power supply voltage. Accordingly, there is a need to temperature-compensate the frequency of an oscillating signal generated by an oscillator used for supply voltage monitoring or other purposes.